Process for manufacturing a soy protein concentrate having high isoflavone content

ABSTRACT

A method for manufacturing a soy protein concentrate having a low non-digestible oligosaccharide and high isoflavone content. The soy protein may have high saponin content. The method includes the use of a membrane in an ultrafiltration process to separate non-digestible oligosaccharides from protein, while retaining isoflavones and saponins with protein. The soy protein concentrate with a low non-digestible oligosaccharide and high isoflavone and saponin content is useful as a milk substitute and in drink mixes as well as an ingredient in other nutrition and health products.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 10/118,764 filed on Apr.18, 2002 now U.S. Pat. No. 6,818,246, which claims the benefit underTitle 35, U.S.C. § 119(e) of U.S. Provisional Patent Application Ser.No. 60/282,520, entitled LOW OLIGOSACCHARIDE SOY PROTEIN CONCENTRATE ANDPROCESS FOR ITS MANUFACTURE, filed on Apr. 9, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a soy protein concentrate that has desirableflavor, functional and nutritional properties.

2. Description of the Related Art

The benefits of soy protein are well documented. Cholesterol is a majorconcern with consumers throughout the industrialized world. It is wellknown that vegetable products contain no cholesterol. For decades,nutritional studies have indicated that the inclusion of soy protein inthe diet actually reduces serum cholesterol levels in people who are atrisk. The higher the cholesterol, the more effective soy proteins are inlowering that level.

Soybeans have the highest protein content of all cereals and legumes. Inparticular, soybeans have about 40% protein, while other legumes have20–30%, and cereals have about 8–15% protein. Soybeans also containabout 20% oil with the remaining dry matter mostly carbohydrate (35%).On a wet basis (as is), soybeans contain about 35% protein, 17% oil, 31%carbohydrates, and 4.4% ash.

In the soybean, both storage protein and lipid bodies are contained inthe usable meat of the soybean (called the cotyledon). The complexcarbohydrate (or dietary fiber) is also contained in the cell walls ofthe cotyledon. The outer layer of cells (called the seed coat) makes upabout 8% of the soybean's total weight. The raw, dehulled soybean is,depending on the variety, approximately 18% oil, 15% solublecarbohydrates, 15% insoluble carbohydrates, 14% moisture and ash, and38% protein.

In processing, soybeans are carefully selected for color and size. Thesoybeans are then cleaned, conditioned (to make removal of the hulleasier) and cracked, dehulled and rolled into flakes. The flakes aresubjected to a solvent bath that removes the oil. The solvent is removedand the flakes are dried, creating the defatted soy flakes that are thebasis of all soy protein products. Despite the large number of productson the market, there are only three types of soy protein products:flours, concentrates and isolates.

Soy flours are high in oligosaccharides and have a “beany” flavor thatmay be objectionable to some consumers. The lack of optimized processingmakes soy flours highly variable in terms of quality.

Soy flours and grits are still widely produced and are used most oftenin baked goods, snack foods and pet foods applications where the highflavor profile does not pose a problem. Textured soy flours were anearly attempt at simulating or enhancing the texture of meat products.Texturizing does not change the composition of soy flours and reducesthe flavor profile only slightly. Their primary applications areinexpensive meat products or pet foods.

The oligosaccharides, raffinose and stachyose, in soy flour potentiallycause flatulence as their bacterial fermentation in the colon createsintestinal gas. Suarez reported that ingestion of 34 grams (g) ofconventional soy flour (1.3 g raffinose and stachyose) caused nosignificant increase in flatulence frequency, whereas ingestion of 80 gof conventional soy flour (3.1 g raffinose and stachyose) resulted in asignificant increase in flatulence frequency. Surarez, Fabrizis L. etal., Am. J. Clin. Nutr., 69:135–9 (1999).

Soy concentrates have at least 65% protein. A myriad of applicationshave been developed for soy concentrates and texturized concentrates inprocessed foods, meat, poultry, fish, cereal and dairy systems. Soyprotein concentrates are made by removing soluble carbohydrate materialfrom defatted soy meal. The most common means for carbohydrate removalis aqueous alcohol extraction (60–80% ethanol) or acid leaching(isoelectric pH 4.5). In both aqueous alcohol extraction and acidleaching, however, essentially all of the protein is rendered insoluble.Protein solubility may be recovered in acid leach products byneutralization.

Isolates are produced through standard chemical isolation, drawing theprotein out of the defatted flake through solubilization (alkaliextraction at pH 7–10) and separation followed by isoelectricprecipitation. As a result, isolates are 90% protein on a moisture-freebasis. They contain no dietary fiber and are sometimes high in sodium,properties that can limit their application. Their major applicationshave been in dairy substitution, as in infant formulas and milkreplacers.

It is known that a soy protein product having a substantially blandtaste and colorless appearance may be produced by filtration using amembrane having a molecular weight cut off (MWCO) of 70,000.

In recent years, researches have been conducted to better understand therole of isoflavones in chronic disease prevention. According to theAmerican Institute for Cancer Research, isoflavones may inhibit enzymesnecessary for the growth and the spread of many types of cancer such asbreast cancer, prostate cancer and colon cancer. Isoflavones also haveshown great promise in preventing osteoporosis and treating menopausalsymptoms.

Soybeans contain about 0.5% by weight saponins. Soy saponins have beenthe subject of investigation since the early 20^(th) century. Thesecompounds consist of a triterpenoid skeleton with various sugar andacetyl moieties. The current consensus is that soyasapogenols A, B and Eare true aglycons, while other soyasapogenols are artifacts ofhydrolysis conditions. The corresponding glycosides are the so-called‘group A saponins’, ‘group B saponins’, and ‘group E saponins’,respectively.

Soy saponins have demonstrated anti-mutagenic properties that make thempromising agents for cancer prophylaxis. Moreover, group B soy saponinshave exhibited pronounced suppressive effects on the replication invitro of the human immunodeficiency virus (HIV). The chemical structureof soybean saponins is very similar to that of the compoundglycyrrhizin, a known anti-viral agent, so soy saponins show promise asbuilding blocks for the synthesis of anti-viral pharmaceuticalcompounds.

SUMMARY OF THE INVENTION

The present invention comprises a soy protein concentrate having lowoligosaccharide and high isoflavone and saponin content. Morespecifically, the present invention comprises a method, using soy flouror soy flakes as a starting material, for producing soy proteinconcentrate having low non-digestible oligosaccharides and highisoflavone and saponin content.

It is an objective of the present invention to produce soy proteinconcentrates having a protein content of more than 70 wt. % and lessthan 90 wt. % of total dry matter, and an isoflavone content of at least2 milligrams/gram (mg/g) of total dry matter.

It is another objective of the present invention to produce soy proteinconcentrates containing a combined raffinose and stachyose content ofless than about 50 mg/g of total dry matter.

It is a further objective of the present invention to produce soyprotein concentrates having a soyasapogenol content of more than 2.0mg/g of total dry matter.

It is yet a further objective of the present invention to produce soyprotein concentrates having a high Nitrogen Solubility Index (NSI).

In one embodiment, the present invention provides a method formanufacturing a soy protein concentrate that comprises the steps of: (a)providing a defatted soybean material, (b) adding water to the materialto form a slurry, (c) removing fiber from the slurry to produce asuspension, and (d) ultrafiltering the suspension using a membranehaving a molecular weight cutoff (MWCO) of up to 30,000. Perferrably, amembrane having a MWCO of between 10,000 and 30,000 is used.Alternatively, a membrane having a MWCO of 1,000,000 may be used toremove oligosaccharides and to produce a product having a proteincontent of at least 70 wt. % of total dry matter and an isoflavonecontent of at least 2 mg/g of total dry matter.

The defatted soybean material may be soy flakes or soy flour. Thedefatted material may contain less than about 1.0 wt. % fat, at least 45wt. % protein and have a protein dispersibility index (PDI) of about 90.The defatted material may further contain about 30 to 40 wt. %carbohydrates, and about 5 to 10 wt. % moisture.

In one specific form of the present invention, an amount of water isadded to the defatted material to produce a slurry that contains about 5to 15 wt. % solids.

In another specific form of the present invention, a membrane having amolecular weight cutoff of 10,000 is used in the step of ultrafilteringthe suspension.

In one specific embodiment, the method for manufacturing a soy proteinconcentrate further comprises the step of recovering a product having aprotein content of at least 70% of total dry matter and an isoflavonecontent of at least 2 mg/g of total dry matter. The product furthercontains a combined raffinose and stachyose content of less than 50 mg/gof total dry matter.

In another embodiment of the present invention, the method formanufacturing a soy protein concentrate includes a step of adjusting thepH of the slurry to at least about 7.0, prior to the step of removingthe fiber. Specifically, the pH of the slurry can be adjusted to betweenabout 7 to about 7.5. More specifically, the pH of the slurry isadjusted by adding sodium hydroxide to the slurry.

In another specific embodiment, the method for manufacturing a soyprotein concentrate further comprises a step of spray drying theproduct.

In yet another specific embodiment, the method for manufacturing a soyprotein concentrate further comprises a step of pasteurizing the productprior to spray drying the product. The step of pasteurizing the productmay be accomplished by jet cooking at a temperature of between about 76°C. and about 130° C.; preferably a temperature of above about 93° C. isused.

In another specific embodiment, the method for manufacturing a soyprotein concentrate further comprises a step of pasteurizing thesuspension prior to the ultrafiltration step.

In a more specific embodiment of the present invention, the method formanufacturing a soy protein concentrate comprises the steps of (a)providing a defatted soybean material, (b) adding water to the materialto form a slurry, wherein the slurry has between about 5 and 15 wt. %solids, (c) adjusting the pH of the slurry to about 7 to 7.5 with sodiumhydroxide, (d) removing fiber from the slurry by centrifugation toproduce a suspension, (e) pasteurizing the suspension by jet cookingabove the 115° C., (f) ultrafiltering the suspension using a membranehaving a molecular weight cutoff (MWCO) of up to 30,000 to produce aretentate, (g) pasteurizing the retentate by jet cooking above about 93°C., (h) spray drying the pasteurized retentate to form a product, and(i) recovering the product having a protein content of at least 70 wt. %of total dry matter and at least 2 mg of isoflavones per g of total drymatter.

In a specific embodiment of the invention, the soy protein concentratecomprises a protein content of at least 70 wt. % of total dry matter andisoflavones of at least 2 mg/g of total dry matter. The soy proteinconcentrate may further comprise a combined raffinose and stachyosecontent of less than 50 mg/g of total dry matter. The soy proteinconcentrate may further comprise a crude fiber of less than 3 wt. % ofdry matter. Further, the soy protein concentrate may comprise asoyasapogenol content of more than about 2.0 mg/g of total dry matter.

DETAILED DESCRIPTION

The present method generally encompasses: 1) dehulling whole soybeans;2) flaking the dehulled soybeans; 3) extracting soybean oil from theflaked soybeans with a solvent; such as hexane; 4) desolventizing thedefatted soybean flakes without high heating or toasting to produce“white” flakes; 5) grinding the flakes to make soy flour; 6) removingfiber from the soy flour and retaining proteins; and 7) ultrafilteringto remove carbohydrates and minerals.

Steps 1 through 4 described above are commonly referred to as theextraction process for soybeans. The general procedure for theabove-described steps 1 through 5 is well understood. See U.S. Pat. No.5,097,017 to Konwinski and U.S. Pat. No. 3,897,574 to Pass, eachassigned to the assignee of the present invention, the disclosures ofwhich are expressly incorporated herein by reference. See also“Extraction of Oil from Soybeans,” J. Am. Oil Chem. Soc., 58, 157 (1981)and “Solvent Extraction of Soybeans,” J. Am. Oil Chem. Soc., 55, 754(1978).

The first step described above is dehulling. Dehulling is the process inwhich the soybean hulls are removed from the whole soybeans. Thesoybeans are carefully cleaned prior to dehulling to remove foreignmatter, so that the final product will not be contaminated by colorbodies. Soybeans also are normally cracked into about 6 to 8 piecesprior to dehulling. The hull typically accounts for about 8% of theweight of the whole soybean. The dehulled soybean is about 10% water,40% protein, 20% fat, with the remainder mainly being carbohydrates,fiber and minerals.

The second step described above is the flaking process. Soybeans areconditioned prior to flaking by adjusting moisture and temperature tomake the soybean pieces sufficiently plastic. The conditioned soybeanpieces are passed through flaking rolls to form flakes of about 0.25 to0.30 millimeters (mm) thick.

The third step described above involves removal of soybean oil from theflakes or defatting. This process is performed by contacting the flakeswith hexane. The oil that is removed by this process may be used inmargarine, shortening and other food products. The soybean oil is also agood source of lecithin, which has many useful applications as anemulsifier.

In the fourth step described above, the hexane-defatted soybean flakesare desolventized to remove hexane, without toasting, to produce whiteflakes. This is different than conventional soybean oil hexane processeswhere the flakes are toasted and used for animal feed.

In the fifth step described above, the white flakes are ground to makesoy flour. Soy flour that can be used as a starting material for thesubject invention is readily, commercially available. Commercial soyflour typically would have at least 50% (52.5%) protein (N×6.25); about30–40% (34.6%) carbohydrates; about 5–10% (6%) moisture; about 5–10%(6%) ash; about 2–3% (2.5%) crude fiber; and less than about 1% (0.9%)fat (ether extract).

The soy flour may have a protein dispersibility index (PDI) of 90. PDIis determined by American Oil Chemist's Society (AOCS) method Ba 10-65.Soy flour having 90 PDI would be soy flour with no heat treatment and isenzyme active. The soy flour may be 80 mesh, which means that more than95 wt. % of the soy flour passes through a number 80 mesh USA standardsieve.

According to one embodiment of the present invention, the startingmaterial, which can be soy flour or soy flakes, is produced according tothe process such as that described in steps 1–5 above.

The next step involves removing fiber from the starting material. Inthis step, an amount of water is added to the starting material to forma slurry. The water may be pre-heated to about 50° C. to about 65° C. Ina specific embodiment, the slurry contains about 5–15 wt. % solids. Itusually is necessary to provide some agitation or mixing to slurry thestarting material. One means for performing the mixing is apropeller-type agitator.

In the step of fiber removal, the pH of the slurry is adjusted to about7–7.5, and more preferably about 7.4. The pH may be adjusted by addingsodium hydroxide to the slurry.

The separation of fiber from the slurry can be performed by any one of anumber of physical separation means, such as by centrifugation using adecanting centrifuge, for example. After the centrifugation, the cakecontaining fiber is separated from the suspension, which is collected.

In one embodiment of this invention, the suspension is pasteurized. Onemeans for pasteurization is jet cooking at a high temperature,preferably, at a temperature of about 93° C. The temperature may reachabout 127° C. In yet another embodiment of this invention, thesuspension may be pasteurized in a steam-jacketed kettle.

In the next step, the suspension is ultrafiltered to removeoligosaccharides and other sugars while retaining isoflavones andsaponins in the retentate. Isoflavones and saponins are small molecularweight components, less than 1500 in molecular weight. Surprisingly,however, it has been found that isoflavones and saponins are retained bythe ultrafiltration membranes in the retentate. It is believed at thistime that the isoflavones and saponins might complex with the proteinssuch that the majority of the isoflavones and saponins are retained inthe retentate. Typically, about 75 wt. % of the feed volume is removedas permeate during the ultrafiltration, resulting in a retentate producthaving a protein content of at least about 70 wt. % of total dry matter.Preferably, the product contains protein at about 75 to 85 wt. % oftotal dry matter.

Any membrane including spiral-wound membranes with a MWCO of up to30,000 is suitable for the ultrafiltration step. Preferably, a membranewith a MWCO of between 10,000 and 30,000 is used. Alternatively, amembrane with a MWCO of 1,000,000 may be used. Spiral-wound membranes ofdifferent MWCO are commercially and readily available. Suitablemembranes are available from, for example, Koch Membrane Systems,Wilmington, Mass.; Osmonics, Minnetonka, Minn.; PTI Advanced Filtration,Oxnard, Calif.; and Synder Filtration, Vacaville, Calif.

During the ultrafiltration step, the temperature of the suspension canbe lowered. One means of lowering the temperature is to include a heatexchanger in the ultrafiltration system and pass cold water through theheat exchanger. The heat exchanger may be installed prior to or after apre-filter for the membrane system or within the membrane system itself.

The ultrafiltered product may be pasteurized before being dried. Onemeans for pasteurization is jet cooking. In yet another embodiment ofthis invention, the product may be pasteurized in a steam-jacketedkettle. The pasteurization is performed so that the product achieves anacceptable microbial profile and tests negative for salmonella. Thepreferred means of drying is a vertical spray dryer with a high-pressurenozzle.

The product is dried to form a soy protein concentrate that containsisoflavones of at least 2 mg/g of total dry matter. The product has lownon-digestible oligosaccharide content; the combined content ofraffinose and stachyose is less than 50 mg/g of total dry matter. Theproduct may further contain a high content of soyasapogenols, which maybe at least about 2.0 mg/g of total dry matter.

The product has many uses. For example, it can be used as a milksubstitute and in drink mixes and beverages, such as chocolate, vanillaand pineapple beverages; dairy products, such as fruit yogurt; nutritionand health products, such as protein bars; whole muscle meat injection;surimi products; emulsified meats; cereal products, such as breakfastcereals; bakery products, such as blueberry muffins and other liquid ordry beverage, food or nutritional products. The dried product may becoated with commercial lecithin or other food-grade surfactants, such asmono-diglycerides, to improve water dispersibility and reduce clumpingof the product.

METHODS AND STANDARDS

1. Nitrogen Solubility Index (NSI) was measured according to AmericanOil Chemists' Method Ba 11-65.

2. Protein Dispensability Index (PDI) was measured according to AmericanOil Chemists' Method Ba 10-65.

3. Isoflavones were characterized by the procedure described inThiagarajan, D. G., Bennink, M. R., Bourquin, L. D., and Kavas, F. A.,Prevention of precancerous colonic lesions in rats by soy flakes, soyflour, genistein, and calcium, Am. J. Clin. Nutr. 1998; 68(suppl);1394S-9S.

4. Saponins were analyzed using HPLC. An HPLC-based analytical methodwas developed and validated to estimate saponin precursors present insoybean. The method is based on isolation of total saponins from finelyground soybean or soybean products using an ethanolic extractionfollowed by acid hydrolysis to cleave the conjugated sugar chain(s) toform their aglycons (soyasapogenols). Resulting soyasapogenols wereisolated and concentrated by solid phase extraction techniques.Soyasapogenols were resolved using a reverse phase column with isocraticelusions and detected using an Evaporative Light Scattering Detector(ELSD). The quantification of soyasapogenols was performed using thecalibration curves derived against authentic compounds. The total soysaponin content is approximately twice the total soyasapogenol content(Duhan et al. (2001) Int. J. Food Sci. Nutr. 52:53–59).

The following non-limiting examples are presented to illustrate theinvention, which is not to be considered as limited thereto. In theexamples and throughout the specification, percentages are by weightunless otherwise indicated.

EXAMPLE 1

About 23 kilograms (50 pounds) of soy flour having a proteindispersibility index (PDI) of 86 was dispersed in 236 kilograms (519pounds) of water to form a slurry. The pH was adjusted to about 7.5using sodium hydroxide. The slurry was mixed for 30 minutes at atemperature of about 60° C., and then centrifuged in a decantingcentrifuge. The insoluble centrifuge cake was discarded, and thesupernatant (suspension) was heat treated by passing through a jetcooker at a temperature of about 121° C. with a holding time of 15seconds. The suspension was then cooled to about 48.8° C. in a jacketedvessel. The suspension was then ultrafiltered using a 10,000 molecularweight cutoff (MWCO) spiral-wound membrane to remove about 75 wt. % ofthe feed volume as permeate. The retentate from the membrane was heattreated by passing though a jet cooker at a temperature about 93° C.with a holding time of 15 seconds. The retentate was then cooled toabout 60° C. in a jacketed vessel and spray dried. The product wasanalyzed to determine the content.

The results from two runs (TABLE 1) show that the product has a proteincontent of between 79.79 and 82.97 wt. % of dry matter. The totalisoflavone content is more than 2 mg/g of total dry matter and acombined amount of raffinose and stachyose is less than 3 wt. %. Inaddition, the NSI of the product was greater than 95% in both runs.

TABLE 1 Composition of product derived from the method of EXAMPLE 1 wt.% Composition Run 1 Run 2 Protein 79.79* 82.97* Moisture 1.23 3.73 Ash(as is) 6.87 6.50 Crude fiber (as is) 0.80 0.80 Monosaccharides (as is)0.13 0.06 Sucrose (as is) 2.88 3.49 Melibiose (as is) 0.00 0.44Raffinose (as is) 0.18 0.32 Stachyose (as is) 1.80 2.40 TotalIsoflavones 2.18** 3.51** Nitrogen Solubility Index (NSI) 96.99 95.45*dry wt basis (wt. %), **dry wt basis (mg/g of total dry matter)

EXAMPLE 2

About 227 liters (60 gallons) of water were added to a mixing tank andheated to 60° C. Then, about 45 kilograms (100 pounds) of soy flakeswere added to the mixing tank to form a slurry. The pH of the slurry wasadjusted to about 7.1, using about 1400 ml of 4.5% NaOH solution. Theslurry was mixed for 10 minutes at a temperature of about 55° to about58° C. and then transferred to a centrifuge feed tank, which containedabout 303 liters (80 gallons) of water preheated to a temperature ofabout 60° C. The diluted slurry was mixed for about 20 minutes at atemperature of about 55° to about 58° C. and thereafter fed at a rate ofabout 7.6 liters (2 gallons) per minute to a Sharples scroll-typecentrifuge. The supernatant (suspension) was jet cooked at a temperatureof about 127° C. The jet-cooked suspension was transferred to a membranefeed tank through a 100-mesh strainer. About 10 grams of sodiummetabisulfite was added to the membrane feed tank. The suspension wasfed to an ultrafiltration membrane system containing a spiral-woundmembrane with a MWCO of 10,000. The temperature of the suspension wasmaintained at about 26.5°–26.8° C. during membrane processing. About 75%of the original feed volume added to the membrane feed tank was removedas permeate. The retentate from the membrane system was pasteurized atabout 76.7° C. and spray dried using a high-pressure pump feeding aspray nozzle in a vertical spray dryer. The dried product was analyzedto determine the content thereof. The results of the analysis are shownin TABLE 2.

TABLE 2 Composition of product derived from the method of EXAMPLE 2 mg/gComposition wt. % of total dry matter protein 82.73 crude fiber 0.94crude fat 0.01 ash 5.91 fructose 2.90 galactose 1.33 sucrose 40.29raffinose 6.88 stachyose 30.13 isoflavones 4.54 daidzin 0.77 glycitin0.22 genistin 1.00 6″-O-malonyldaidzin 0.91 6″-O-malonylglycitin 0.166″-O-acetyl genistin 0.12 6″-O-malonylgenistin 1.24 daidzein 0.05genistein 0.07 soyasapogenols 4.06 soyasapogenol A 1.25 soyasapogenol B2.81 Nitrogen Solubility Index (NSI) 92

EXAMPLE 3

About 227 liters (60 gallons) of water were added to a mixing tank andheated to a temperature of about 60° C. Then, about 45 kilograms (100pounds) of soy white flakes were added to the mixing tank to form aslurry. The pH of the slurry was adjusted to about 7.08, using about1400 ml of 4.5% NaOH solution. The slurry was mixed for 10 minutes at atemperature of about 55° to about 58° C. and then transferred to acentrifuge feed tank, which contained about 303 liters (80 gallons) ofwater preheated to a temperature of about 60° C. The diluted slurry wasmixed for about 20 minutes at a temperature of about 55° to about 58° C.and thereafter fed at a rate of about 7.6 liters (2 gallons) per minuteto a Sharples scroll-type centrifuge. The supernatant (suspension) wasjet cooked at a temperature of about 127° C. The jet-cooked suspensionwas transferred to a membrane feed tank through a 100-mesh strainer. Thesuspension was fed to an ultrafiltration membrane system containing aspiral-wound membrane with a MWCO of 10,000. The temperature of thesuspension was maintained at about 48.8° to about 49° C. during membraneprocessing. About 75% of the original feed volume added to the membranefeed tank was removed as permeate. The retentate from the membranesystem was pasteurized at a temperature of about 76.7° C. and spraydried using a high-pressure pump feeding a spray nozzle in a verticalspray dryer. The dried product was analyzed to determine the contentthereof. The results of the analysis are shown in TABLE 3.

TABLE 3 Composition of product derived from the method of EXAMPLE 3 mg/gComposition wt. % of total dry matter protein 82.81 crude fiber 0.84crude fat 0.13 ash 6.00 fructose 2.72 galactose 1.21 sucrose 30.11raffinose 4.99 stachyose 21.80 isoflavones 3.54 daidzin 0.67 glycitin0.09 genistin 0.90 6″-O-malonyldaidzin 0.61 6″-O-malonylglycitin 0.086″-O-acetyl genistin 0.16 6″-O-malonylgenistin 0.96 daidzein 0.03genistein 0.04 soyasapogenols 3.98 soyasapogenol A 1.05 soyasapogenol B2.93 Nitrogen Solubility Index (NSI) 93.8

EXAMPLE 4

About 227 liters (60 gallons) of water were added to a mixing tank andheated to a temperature of about 60° C. Then, about 45 kilograms (100pounds) of soy flour were added to the mixing tank to form a slurry. ThepH of the slurry was adjusted to about 7.08, using about 1400 ml of 4.5%NaOH solution. The slurry was mixed for 10 minutes at a temperature ofabout 55° to about 58° C. and then transferred to a centrifuge feedtank, which contained about 303 liters (80 gallons) of water preheatedto a temperature of about 60° C. The diluted slurry was mixed for about20 minutes at a temperature of about 55° to about 58° C. and thereafterfed at a rate of about 7.6 liters (2 gallons) per minute to a Sharplesscroll-type centrifuge. The supernatant (suspension) was jet cooked at atemperature of about 127° C. The jet-cooked suspension was transferredto a membrane feed tank through a 100-mesh strainer. The suspension wasfed to an ultrafiltration membrane system containing a spiral-woundmembrane with a MWCO of 30,000. The temperature of the suspension wasmaintained at about 48.8° to about 49° C. during membrane processing.About 75% of the original feed volume added to the membrane feed tankwas removed as permeate. The retentate from the membrane system waspasteurized at a temperature of about 76.7° C. and spray dried using ahigh-pressure pump feeding a spray nozzle in a vertical spray dryer. Thedried product was analyzed to determine the content thereof. The resultsof the analysis are shown in TABLE 4.

TABLE 4 Composition of product derived from the method of EXAMPLE 4 mg/gComposition wt. % of total dry matter protein 82.31 crude fiber 1.14crude fat 0.01 ash 5.44 fructose 2.79 galactose 1.60 sucrose 33.14raffinose 5.88 stachyose 24.24 isoflavones 3.53 daidzin 0.60 glycitin0.17 genistin 0.70 6″-O-malonyldaidzin 0.76 6″-O-malonylglycitin 0.116″-O-acetyl genistin 0.09 6″-O-malonylgenistin 0.99 daidzein 0.04genistein 0.07 soyasapogenols 3.74 soyasapogenol A 1.04 soyasapogenol B2.70 Nitrogen Solubility Index (NSI) 89.2

EXAMPLE 5

About 227 liters (60 gallons) of water were added to a mixing tank andheated to a temperature of about 60° C. Then, about 45 kilograms (100pounds) of soy flour were added to the mixing tank to form a slurry. ThepH of the slurry was adjusted to about 7.0, using about 1400 ml of 4.5%NaOH solution. The slurry was mixed for 10 minutes at a temperature ofabout 55° to about 58° C. and then transferred to a centrifuge feedtank, which contained about 303 liters (80 gallons) of water preheatedto a temperature of about 60° C. The diluted slurry was mixed for about20 minutes at a temperature of about 55° to about 58° C. and thereafterfed at a rate of about 7.6 liters (2 gallons) per minute to a Sharplesscroll-type centrifuge. The supernatant (suspension) was jet cooked at atemperature of about 127° C. The jet-cooked suspension was transferredto a membrane feed tank through a 100-mesh strainer. The suspension wasfed to an ultrafiltration membrane system containing a spiral-woundmembrane with a MWCO of 1,000,000. The temperature of the suspension wasmaintained at about 48.8° to about 49° C. during membrane processing.About 75% of the original feed volume added to the membrane feed tankwas removed as permeate. The retentate from the membrane system waspasteurized at a temperature of about 76.7° C. and spray dried using ahigh-pressure pump feeding a spray nozzle in a vertical spray dryer. Thedried product was analyzed to determine the content thereof. The resultsof the analysis are shown in TABLE 5.

TABLE 5 Composition of product derived from the method of EXAMPLE 5 mg/gComposition wt. % of total dry matter protein 82.32 crude fiber 1.25crude fat 0.07 ash 5.72 fructose 2.78 galactose 1.38 sucrose 36.44raffinose 6.82 stachyose 26.07 isoflavones 3.37 daidzin 0.54 glycitin0.16 genistin 0.69 6″-O-malonyldaidzin 0.74 6″-O-malonylglycitin 0.116″-O-acetyl genistin 0.10 6″-O-malonylgenistin 0.98 daidzein 0.02genistein 0.03 soyasapogenols 3.55 soyasapogenol A 1.04 soyasapogenol B2.51 Nitrogen Solubility Index (NSI) 90.7

1. A method for producing a soy protein concentrate, comprising thesteps of: (a) providing a substantially defatted soybean material; (b)mixing the material with water and extracting proteins from thematerial; (c) removing insoluble materials to produce a liquor; (d) heattreating the liquor at a temperature above 93° C.; and (e) subjectingthe liquor to ultrafiltration using an ultrafiltration membrane having amolecular weight cutoff of up to 30,000 to provide a retentate; (f)optionally pasteurizing the retentate; and (g) drying the retentate toprovide a soy protein concentrate.
 2. The method of claim 1, wherein theultrafiltration of said step (e) is conducted at a temperature ofbetween about 25° C. and about 50° C.
 3. The method of claim 1, whereinthe soy protein concentrate includes a protein content of between about70.0 wt. % and about 85.0 wt. % of total dry matter; an isoflavonescontent of at least about 2.0 mg/g of total dry matter; and a crudefiber content of less than about 3.0 wt. % of total dry matter.
 4. Themethod of claim 1, wherein the soy protein concentrate includes aprotein content of between about 70.0 wt. % and about 85.0 wt. % oftotal dry matter; a soyasapogenols content of at least about 2.0 mg/g oftotal dry matter; and a crude fiber content of less than about 3.0 wt. %of total dry matter.
 5. The method of claim 1, wherein theultrafiltration of said step (d) is conducted using an ultrafiltrationmembrane having a molecular weight cutoff of between about 10,000 andabout 30,000.
 6. The method of claim 1, wherein said step (b) furthercomprises adjusting the pH of the mixture to at least about 7.0.
 7. Themethod of claim 1, wherein said step (b) further comprises adjusting thepH of the mixture to between about 7.0 and about 7.5.
 8. The method ofclaim 1, wherein at least one of said steps (d) and (f) is conducted byjet cooking at a temperature above about 93° C.
 9. The method of claim1, wherein the mixture in said step (b) contains from about 5.0 wt. % toabout 15.0 wt. % solids.
 10. The method of claim 1, wherein the soyprotein concentrate contains a combined raffinose and stachyose contentof less than about 50.0 mg/g of total dry matter.
 11. The method ofclaim 1, wherein the substantially defatted soybean material containsless than about 1.0 wt. % fat, and has a Protein Dispersibility Index(“PDI”) of about
 90. 12. The method of claim 1, wherein thesubstantially defatted soybean material contains about 30.0 wt. % toabout 40.0 wt. % carbohydrates and about 5.0 wt. % to about 10.0 wt. %moisture.
 13. A method for producing a soy protein concentrate,comprising the steps of: (a) providing a substantially defatted soybeanmaterial; (b) mixing the material with water and extracting proteinsfrom the material; (c) removing insoluble materials to produce a liquor;(d) subjecting the liquor to ultrafiltration using an ultrafiltrationmembrane having a molecular weight cutoff of up to 30,000 at atemperature of between about 25° C. and about 5° C. to provide aretentate; (e) optionally pasteurizing the retentate; and (f) drying theretentate to provide a soy protein concentrate.
 14. The method of claim13, further comprising the additional step, prior to said step (d), of:heat treating the liquor at a temperature above about 93° C.
 15. Themethod of claim 14, wherein at least one of said step (d) and said heattreatment step is conducted by jet cooking at a temperature above about93° C.
 16. The method of claim 13, wherein the soy protein concentrateincludes a protein content of between about 70.0 wt. % and about 85.0wt. % of total dry matter; an isoflavones content of at least about 2.0mg/g of total dry matter; and a crude fiber content of less than about3.0 wt. % of total dry matter.
 17. The method of claim 13, wherein thesoy protein concentrate includes a protein content of between about 70.0wt. % and about 85.0 wt. % of total dry matter; a soyasapogenols contentof at least about 2.0 mg/g of total dry matter; and a crude fibercontent of less than about 3.0 wt. % of total dry matter.
 18. The methodof claim 13, wherein the ultrafiltration of said step (d) is conductedusing an ultrafiltration membrane having a molecular weight cutoff ofbetween about 10,000 and about 30,000.
 19. The method of claim 13,wherein said step (b) further comprises adjusting the pH of the mixtureto at least about 7.0.
 20. The method of claim 13, wherein said step (b)further comprises adjusting the pH of the mixture to between about 7.0and about 7.5.
 21. The method of claim 13, wherein the mixture in saidstep (b) contains from about 5.0 wt. % to about 15.0 wt. % solids. 22.The method of claim 13, wherein the soy protein concentrate contains acombined raffinose and stachyose content of less than about 50.0 mg/g oftotal dry matter.
 23. The method of claim 13, wherein the substantiallydefatted soybean material contains less than about 1.0 wt. % fat, andhas a Protein Dispersibility Index (“PDI”) of about
 90. 24. The methodof claim 13, wherein the substantially defatted soybean materialcontains about 30.0 wt. % to about 40.0 wt. % carbohydrates and about5.0 wt. % to about 10.0 wt. % moisture.